diff --git a/src/index.ts b/src/index.ts
index 7ce6c7f..e3b2c1e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -15,4 +15,6 @@ export { PendingRequestMap, buildCallHandler } from "./call.js";
 export type { CallEventMap, CallEventMapValue, CallRequestedEvent, CallRespondedEvent, CallAbortedEvent, CallErrorEvent, CallHandler, CallHandlerConfig } from "./call.js";
 export { subscribe } from "./subscribe.js";
 export { createMCPClient, closeMCPClient, MCPClientLoader } from "./from_mcp.js";
-export type { MCPClientConfig, MCPClientWrapper } from "./from_mcp.js";
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+export type { MCPClientConfig, MCPClientWrapper } from "./from_mcp.js";
+export { ResponseEnvelopeSchema, ResponseMetaSchema, RESPONSE_SOURCES, isResponseEnvelope, localEnvelope, httpEnvelope, mcpEnvelope, unwrap } from "./response-envelope.js";
+export type { ResponseEnvelope, ResponseMeta, ResponseSource, LocalResponseMeta, HTTPResponseMeta, MCPResponseMeta, MCPContentBlock, MCPResourceContent, MCPAnnotations } from "./response-envelope.js";
\ No newline at end of file
diff --git a/src/response-envelope.ts b/src/response-envelope.ts
new file mode 100644
index 0000000..7e043f7
--- /dev/null
+++ b/src/response-envelope.ts
@@ -0,0 +1,154 @@
+import { Type, type Static } from "@alkdev/typebox";
+
+export type ResponseSource = "local" | "http" | "mcp"
+
+export interface LocalResponseMeta {
+  source: "local"
+  operationId: string
+  timestamp: number
+}
+
+export interface HTTPResponseMeta {
+  source: "http"
+  statusCode: number
+  headers: Record<string, string>
+  contentType: string
+}
+
+export type MCPContentBlock =
+  | { type: "text"; text: string; annotations?: MCPAnnotations }
+  | { type: "image"; data: string; mimeType: string; annotations?: MCPAnnotations }
+  | { type: "audio"; data: string; mimeType: string; annotations?: MCPAnnotations }
+  | { type: "resource"; resource: MCPResourceContent; annotations?: MCPAnnotations }
+  | { type: "resource_link"; uri: string; name: string; description?: string; mimeType?: string }
+
+export interface MCPResourceContent {
+  uri: string
+  mimeType?: string
+  text?: string
+  blob?: string
+}
+
+export interface MCPAnnotations {
+  audience?: Array<"user" | "assistant">
+  priority?: number
+  lastModified?: string
+}
+
+export interface MCPResponseMeta {
+  source: "mcp"
+  isError: boolean
+  content: MCPContentBlock[]
+  structuredContent?: Record<string, unknown>
+  _meta?: Record<string, unknown>
+}
+
+export type ResponseMeta = LocalResponseMeta | HTTPResponseMeta | MCPResponseMeta
+
+export interface ResponseEnvelope<T = unknown> {
+  data: T
+  meta: ResponseMeta
+}
+
+const LocalResponseMetaSchema = Type.Object({
+  source: Type.Literal("local"),
+  operationId: Type.String(),
+  timestamp: Type.Number(),
+})
+
+const HTTPResponseMetaSchema = Type.Object({
+  source: Type.Literal("http"),
+  statusCode: Type.Number(),
+  headers: Type.Record(Type.String(), Type.String()),
+  contentType: Type.String(),
+})
+
+const MCPAnnotationsSchema = Type.Object({
+  audience: Type.Optional(Type.Array(Type.Union([Type.Literal("user"), Type.Literal("assistant")]))),
+  priority: Type.Optional(Type.Number()),
+  lastModified: Type.Optional(Type.String()),
+})
+
+const MCPResourceContentSchema = Type.Object({
+  uri: Type.String(),
+  mimeType: Type.Optional(Type.String()),
+  text: Type.Optional(Type.String()),
+  blob: Type.Optional(Type.String()),
+})
+
+const MCPContentBlockSchema = Type.Union([
+  Type.Object({
+    type: Type.Literal("text"),
+    text: Type.String(),
+    annotations: Type.Optional(MCPAnnotationsSchema),
+  }),
+  Type.Object({
+    type: Type.Literal("image"),
+    data: Type.String(),
+    mimeType: Type.String(),
+    annotations: Type.Optional(MCPAnnotationsSchema),
+  }),
+  Type.Object({
+    type: Type.Literal("audio"),
+    data: Type.String(),
+    mimeType: Type.String(),
+    annotations: Type.Optional(MCPAnnotationsSchema),
+  }),
+  Type.Object({
+    type: Type.Literal("resource"),
+    resource: MCPResourceContentSchema,
+    annotations: Type.Optional(MCPAnnotationsSchema),
+  }),
+  Type.Object({
+    type: Type.Literal("resource_link"),
+    uri: Type.String(),
+    name: Type.String(),
+    description: Type.Optional(Type.String()),
+    mimeType: Type.Optional(Type.String()),
+  }),
+])
+
+const MCPResponseMetaSchema = Type.Object({
+  source: Type.Literal("mcp"),
+  isError: Type.Boolean(),
+  content: Type.Array(MCPContentBlockSchema),
+  structuredContent: Type.Optional(Type.Record(Type.String(), Type.Unknown())),
+  _meta: Type.Optional(Type.Record(Type.String(), Type.Unknown())),
+})
+
+export const ResponseMetaSchema = Type.Union([
+  LocalResponseMetaSchema,
+  HTTPResponseMetaSchema,
+  MCPResponseMetaSchema,
+])
+
+export const ResponseEnvelopeSchema = Type.Object({
+  data: Type.Unknown({ description: "Operation output" }),
+  meta: ResponseMetaSchema,
+})
+
+export const RESPONSE_SOURCES = ["local", "http", "mcp"] as const
+
+export function isResponseEnvelope(value: unknown): value is ResponseEnvelope {
+  if (typeof value !== "object" || value === null) return false
+  const obj = value as Record<string, unknown>
+  if (!("data" in obj) || !("meta" in obj)) return false
+  if (typeof obj.meta !== "object" || obj.meta === null) return false
+  return RESPONSE_SOURCES.includes((obj.meta as ResponseMeta).source as ResponseSource)
+}
+
+export function localEnvelope<T>(data: T, operationId: string): ResponseEnvelope<T> {
+  return { data, meta: { source: "local", operationId, timestamp: Date.now() } }
+}
+
+export function httpEnvelope<T>(data: T, meta: Omit<HTTPResponseMeta, "source">): ResponseEnvelope<T> {
+  return { data, meta: { source: "http", ...meta } }
+}
+
+export function mcpEnvelope<T>(data: T, meta: Omit<MCPResponseMeta, "source">): ResponseEnvelope<T> {
+  return { data, meta: { source: "mcp", ...meta } }
+}
+
+export function unwrap<T>(envelope: ResponseEnvelope<T>): T {
+  return envelope.data
+}
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